1. Field of the Invention
The present invention is related to an apparatus for identifying the address in a pregroove (ADIP) of a Blu-ray disc, and more particularly, to an apparatus that uses a statistical scheme or distance-finding scheme to determine the position of a predetermined minimum shift keying (MSK) mark in an ADIP unit to identify data of the ADIP unit.
2. Description of Related Art
Conventionally, optical discs, such as digital versatile disc (DVD) and video compact disc (VCD), are extensively applied for business activities or family life. They are mainly used to record bulk data, e.g. movie, music or application software. Recently, in order to increase the storage capacity, a standard for Blu-ray disc was issued to fulfill the requirements of consumers. A Blu-ray disc has more than five times the capacity of DVD.
Reference is made to FIG. 1A, which is a schematic diagram of a conventional optical disc. Generally, in the manufacture process, a spiral pregroove 1 is disposed on the optical disc to define the physical address for data recording. In FIG. 1.B, a portion 2 of the pregroove 1 is magnified. As shown in the figure, the pregroove 1 has a wobble with a specific phase or frequency to define the physical address.
In accordance with the standard of Blu-ray disc, the pregroove has multiple ADIP units with MSK marks and the relative positions of the MSK marks can be used to identify the data in the ADIP units. Thereby, an optical disc drive can determine the physical address of the Blu-ray disc and perform a reading or writing process.
Reference is made to FIG. 2, which is a schematic diagram of an ADIP word in the Blu-ray disc. As shown in the figure, the ADIP word has 83 ADIP units, which are designated as ADIP No. 0-82. Each of the ADIP unit has 56 nominal wobble length (NWL) units, which are designated as Wobble Nos. 0-55. The ADIP word has a word sync unit formed by ADIP No. 1, 3, 5, 7 and each of the ADIP unit has a bit sync unit formed by Wobble No. 0-2.
There are four kinds of wobble structures, designated as “0-3”, for defining the content of the NWL units. The NWL units designated as “0” have a monotone wobble and every three consecutive NWL units designated as “1-3” form an MSK wobble, i.e. an MSK mark.
Reference is made to FIG. 3, which is a schematic diagram of NWL units in accordance with the Blu-ray disc standard. The NWL units designated as “0” have a wobble frequency fwod and a wobble waveform cos(2π*fwod*t). The MSK mark includes three consecutive NWL units, designated as “1-3”, which respectively have wobble frequencies 1.5*fwod, fwod and 1.5*fwod and wobble waveforms cos(2π*(1.5*fwod)*t), −cos(2π*fwod*t) and −cos(2π*(1.5*fwod)*t).
Reference is made again to FIG. 2. The ADIP word has seven kinds of ADIP units, including isolated, sync0, sync1, sync2, sync3, data“0” and data“1” units. The isolated unit only has an MSK mark; the sync “0-1” units have three MSK marks; and the data“0-1” units have two MSK marks.
It should be noticed that the spacing between any two consecutive MSK marks is specific. For example, the spacing having ten NWLs between two consecutive MSK marks only appears in the word sync units, i.e. ADIP No. 1, 3, 5, 7; the spacing having twelve NWLs between two consecutive MSK marks only appears in the data“1” units; and the spacing having fourteen NWLs between two consecutive MSK marks only appears in the data“0” units.
According to this property, the prior art uses the relative positions of the MSK marks to identify the data in the ADIP units. The conventional optical disc drive can determine the physical address and perform a reading or writing process.
However, once a position determination error occurs, the conventional optical disc drive will erroneously determine the spacing between the present and the previous MSK marks and the spacing between the present and the following MSK marks. In other words, the prior art has an error propagation effect and that increases the error probability for data identification of ADIP units.
Accordingly, as discussed above, the prior art still has some drawbacks that could be improved. The present invention aims to resolve the drawbacks in the prior art.